So much so that she was copping a lot of the blame from fans, which forced her to disable her comments on Instagram.
Shortly after, she posted a silent tribute to Mac by sharing a snap of him with no caption, but now we know how she actually reacted when she found out about the tragic news.
According to People magazine, she was "distraught" over his passing.
"She completely broke down after she found out about Mac," a source tells the mag. "She can’t believe he isn’t here anymore. He was such a special person to her. She is very, very sad. This is a nightmare for her."
While many fans blamed her quick engagement to Pete for Mac's overdose, his close pal Shane Powers a revealed how "unbelievably involved and helpful" Ariana was in helping Mac's sobriety while they were dating.
"They were very much in love and I have to say, she was incredible when he was first sobering up," he said on his podcast, The Shane Show. "She was a f*cking G to him. There could not have been anybody more supportive of him being sober than Ariana. I saw that, I was around it, I took phone calls from her. ‘How do I help? What do I do?’ This little girl was unbelievably involved and helpful to him being healthy."
He continued, "there was no one in his life more ready to go to the wall for him when it came to him being sober. She was an unbelievably stabilizing force in his life and she was deeply helpful and effective in keeping Mac sober and helping him get sober. She was all about him being healthy. Period."
Rest in peace.